A cooking oven that has both convection and impingement modes is shown in U.S. Pat. No. 5,345,923 as a countertop oven with one or more removable air impingement supply structures. Each air impingement supply structure includes a specially designed food rack disposed between upper and lower corrugated impingement air forming walls. The air impingement supply structures are removably inserted into the oven's air impingement supply structure cooking chamber for operation in the impingement mode. One or more of the air impingement supply structures can be removed and replaced by a standard food rack for operation in a convection mode. The countertop oven requires n specially designed food racks for n air impingement supply structures and up to n standard food racks. The countertop oven also uses a fan disposed adjacent a side wall of the oven chamber, which increases the side-to-side footprint of the oven.
A cooking oven that has both a microwave mode and an impingement mode is shown in U.S. Pat. No. 5,254,823 as an oven that has a rather large preheated thermal reservoir (at least 60 pounds) so as to facilitate rapid heat transfer to ambient air in a plenum. However, such an oven is quite heavy and cumbersome for many applications. Moreover, the preheat time is considerable (up to two or more hours) and cooling of the oven's exterior surfaces can be difficult and energy inefficient. The oven uses impingement air from a top of the oven's cooking chamber. This will brown or crisp the top of a food product but not the sides or bottom because the browning effect of the impingement jets is lost when the impingement jets merge to form a blanket or are reflected from oven chamber surfaces. The oven has a single microwave energy feed into the bottom of the cooking chamber. This results in uneven microwave cooking as the bottom of the food product is exposed to direct microwave energy and the top of the food is exposed to indirect microwave energy. Moreover, if metal pans are used, bottom feed microwave energy results in a large amount of reflected microwave energy to the bottom feed aperture, which can considerably reduce the useful life of the magnetrons.
There is a need for an oven that can cook food with microwave energy, impingement air and/or convection air.
There is a need for a microwave oven that can use metal pans with improved useful life of the magnetrons.
There is a further need for a light weight oven that has a small footprint.